A portable electronic object, such as an electronic device or, for example, a portable timepiece includes a case generally formed of a middle part closed by a back cover and by a glass. Inside the case is arranged a timepiece movement, which may be totally mechanical or electronic. This timepiece movement is arranged to provide time information, said time information being displayed via analogue or digital display means. The timepiece further includes control means enabling the user to interact with said timepiece.
In general, the control means take the form of push buttons or a crown acting mechanically on said timepiece movement. These push buttons and crowns may be supplemented by a touch interface. This touch interface is used to improve the interactivity of the timepiece and simplify handling especially when the timepiece proposes a significant number of menus and functions. This touch interface may also contribute to the improvement of the aesthetic appearance of the product by removing the usual external protrusions of a crown or push-buttons.
The touch interface may be a resistive touch interface or a capacitive touch interface. For the case of a capacitive touch interface, this may take the form of an electrode placed on the lower face of the glass, the glass being an electrically non-conductive element. The electrode is subjected to an electric field. When the user wishes to activate the interface, he exerts a contacts the external face of the glass, preferably with his finger. This means that the contact can be a tap or a light touch. This contact causes an additional capacitance to appear, formed between said electrode and the finger which is an electrically conductive element. This variation in capacitance is detected by the electronic timepiece movement which will act according to its programming. This touch interface is created on the watch glass and not on the case since the latter is generally made of metal and is therefore electrically conductive. The case does not permit a capacitance to appear.
However, these touch interfaces arranged on the timepiece glass have drawbacks.
A first drawback of arranging the touch interface on the glass is that it does not provide optimum visibility of information. Indeed, the fact of having a touch interface arranged on the timepiece glass means that the user has to regularly place his fingers on the glass. Consequently, the visibility of the information displayed on the dial is regularly hindered by the user's fingers. The user therefore has more difficulty in reading the information provided by the timepiece.
Another drawback is that having a touch interface associated with conventional control elements such as push-buttons or crowns makes the timepiece more complex. Indeed, the fact of having a multitude of buttons in addition to the touch interface results in a larger number of combinations between the buttons and touch interface. The timepiece is therefore more complex to operate.
Another drawback is that for timepieces with a dark dial or a negative contrast display with a dark background, regularly placing fingers on the glass leaves traces (grease, sweat, . . . ) which reduces the attractiveness of the product (like a window covered in fingerprints).